1. Technical Field
The present invention is related to a system for selecting a transmission mode and a method thereof. Particularly, the present invention is related to a system for selecting a transmission mode under the multi-input multi-output (MIMO) architecture based on a scheduling number and a method thereof.
2. Related Art
In response to rapid growth and necessity of high speed wireless networks, particularly the multi-media applications, multicasting systems have been widely employed. As a current multicasting system is concerned, two architectures are included: single-input single-output (SISO) and multi-input multi-output (MIMO).
In the SISO multicasting system, to guarantee a scheduling number, a common way is to use a modulation coding associated with the client with worst channel condition as a basis to conduct a data transmission process, so as to be received the data by as many client ends as the system can.
However, the SISO architecture may cause a rapid reduction of spectral efficiency of the multicasting system, which is compared to the MIMO system case where the multicasting system may select a transmission mode between a spatial diversity (SD) and a spatial multiplexing (SM) based on a scheduling number and the spectral efficiency. The SM mode can promote the transmission efficiency of the system by transmitting different data streams on multiple antennas. On the other hand, the SD mode encodes the signals spatiotemporally and transmits data stream associated therewith, thereby promoting a signal to noise ratio (SNR) of the received signal, and promotes a reliability of the system.
Although there have been some algorithms proposed for a theoretical communication capacity of the MIMO multicasting system, such as the one, by J. Xu, IEEE Trans. on Broadcasting, vol. 56, the scheduling rate factor is not considered and thus not appropriate for the real operations. In addition, algorithms for automatically switching modes and modulation coding have also been proposed for the MIMO system, such as the one, by C. Kim and J. Lee, 2008, but the scheduling rate factor is still absent.
In view of the above, there is a need to improve the state under the MIMO multicasting system where the transmission mode cannot be selected according simultaneously to the spectral efficiency and the scheduling rate, which may be long-felt and needs to be satisfied.